Plasma processing apparatus and method, and plasma control unit

ABSTRACT

[Object] It is an object of the present invention to readily replace a plasma control member disposed to surround a substrate to control plasma in case of plasmarizing a processing gas in the processing vessel by using a high frequency power and performing a substrate on a susceptor by using the plasma.  
     [Constitution of the Invention] A plasma control sheet whose, e.g., rear surface is coated with an adhesive is detachably attached to a ring member provided to surround a substrate mounted on a susceptor. In this case, attachment/detachment of the sheet is carried out with ease so that the burden of an operator is decreased and an operation rate of the apparatus is increased.

FIELD OF THE INVENTION

The present invention relates to a plasma processing apparatus andmethod for performing, for example, an etching process on a substratesuch as a semiconductor wafer by using plasma, and a plasma controlmember employed therein.

BACKGROUND OF THE INVENTION

In a manufacturing process for a semiconductor device, a dry etching ora film forming process is performed on a substrate, for example, asemiconductor wafer (hereinafter, referred to as “wafer”) by usingplasma in order to split up capacitors or devices or otherwise to formcontact holes. One of the various apparatuses for performing such plasmaprocesses is a single sheet parallel plate type plasma processingapparatus for generating plasma by applying a high frequency voltagebetween an upper and a lower electrode.

FIG. 1 shows a schematic configuration view of a single sheet parallelplate type plasma processing apparatus. An airtight vessel 2 serving asa vacuum chamber includes an upper electrode 11 which also serves as agas shower head, a lower electrode 12 which also serves as a susceptormounting thereon a substrate, and a focus ring 13 disposed to surround awafer 100 mounted on the lower electrode (susceptor) 12, the focus ring13 being formed of, for example, quartz. Reference numeral 14 is anelectrostatic chuck for attracting and holding the wafer 100electrostatically. Embedded in the electrostatic chuck 14 is a thin filmshaped electrode 15 to which a chuck voltage from a power supply (notshown) is applied. A predetermined processing gas which is selectedbased on the type of processing to be performed is sprayed toward thewafer 100 from the gas shower head (upper electrode) 11 while theairtight vessel 1 is evacuated by means of a vacuum pump 16 such thatthe internal pressure thereof is maintained at a preset pressure level.Then, by applying a high frequency power between the upper electrode 11and the lower electrode 12 from a high frequency power supply 17, theprocessing gas is converted into plasma to thereby perform apredetermined process, e.g., etching the wafer 100.

Since the processing gas reaching the vicinity of the surface of thewafer 100 is exhausted from the periphery of the wafer 100 downwardlyand outwardly, the flow of the processing gas in the peripheral portionof the wafer 100 differs from that in the central portion thereof. As aresult, at the peripheral portion of the wafer 100, the predeterminedcomposition balance of the processing gas is disturbed, and theimpedance or conductance components between the plasma and the lowerelectrode 12 in the region where the wafer 100 is placed deviate fromthose in the peripheral region located outer than that. Specifically,the dissociation level of the processing gas is higher in the peripheralportion of the wafer 100, which is closer to a gas exhaust space, thanin the central portion of the wafer 100. Accordingly, the density of theplasma in the vicinity of the peripheral portion of the wafer 100becomes higher, so that the etching rate of the peripheral portion ofthe wafer 100 becomes higher than that of the central portion, thuscausing non-uniform etching over different parts of the wafer 100.

Meanwhile, to maximize utilizing the wafer 100 efficiently, devices needto be formed in part of the wafer 100 as close to its outer edge aspossible. Thus, etching rates should be uniform throughout the centralportion of the wafer 100 and its peripheral portion. For the purpose,the focus ring 13 made of, for example, a conductor, a semiconductor ora dielectric material is disposed to surround the wafer 100, to therebycontrol the density of plasma above the peripheral portion of the wafer100. Specifically, the material for the focus ring 13 is selecteddepending on the kind of the processing gas or the material of the filmto be etched, in order to install the focus ring 13 adequately for theprocess to be performed. For example, Patent Reference 1 discloses thatin case of etching a refractory metal and its silicide (siliconcompound) by using chlorine radicals generated by plasmarization, SiC isa preferable material for the focus ring 13 since it can mitigate therise of chlorine radical concentration at the peripheral portion of thewafer 100 due to its strong tendency to adsorb chlorine radicals.

Further, for example, Patent Reference 2 discloses that, when using aquartz ring as the focus ring 13 serving as an insulator, the surface ofthe quartz ring is coated with, for instance, polyimide to preventrelease of oxygen from the surface of the quart ring, which affectsetching characteristics.

[Reference Patent 1] Japanese Patent Laid-open Publication No. 62-47130

[Reference Patent 2] Japanese Patent Laid-open Publication No. 11-317393

DISCLOSURES OF THE INVENTION Object of the Invention

As desired patterns become progressively finer, however, a furtherimprovement of in-surface uniformity of the wafer 100 is required whencarrying out an in-surface treatment of the wafer 100. The method usingthe adsorption of chlorine radicals disclosed in Reference Patent 1,however, cannot satisfy the recent demands for even finer designspecifications. That is to say, the method cannot suppress the increasein etching rate at the peripheral portion of the wafer 100 sufficiently.As a solution to the problem, the inventors of the present inventionhave considered using carbon to fabricate a focus ring. In case thefocus ring 13 is formed of carbon and is exposed to plasma during aplasma processing, carbon radicals and the like are dissociated from thecarbon and thereafter react with chlorine radicals to consume them.Therefore, the density of chlorine radicals around the peripheralportion of the wafer 100 can be reduced. However, since carbon becomesdamaged by being exposed to plasma, the focus ring needs to be replacedperiodically, for example, every 1000 hours, and the manufacturing costthereof is increased due to the cost of carbon rings.

Moreover, as in Reference Patent 2, in case of coating the surface ofthe focus ring 13 with polyimide to thereby form a polyimide layer onthe surface of the focus ring 13, the polyimide may be degraded astreatment of the wafer 100 is repeated. In such a case, the focus ring13 needs to be separated from the apparatus to remove the degradedpolyimide therefrom and coat it with a new polyimide layer again, whichis labor intensive and troublesome.

It is, therefore, an object of the present invention to provide a plasmaprocessing apparatus and method capable of readily replacing a plasmacontrol member disposed to surround a substrate to control plasma.

CONSTITUTIONS OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided a plasma processing apparatus for converting a processing gasinto a plasma by a high frequency power to perform a process on asubstrate mounted on a susceptor by using the plasma in a processingvessel, the apparatus including a ring member disposed to surround thesubstrate on the susceptor; a plasma control sheet disposed on a surfaceof the ring member; and an adhesion layer, interposed between the ringmember and the plasma control sheet, for allowing the plasma controlsheet to be detachably attached to the ring member.

The adhesion layer may be an adhesive coated on a rear surface of theplasma control sheet. Further, the plasma control sheet may contain amaterial for dissociating a component which reacts with a primary activespecies for the plasma processing. Moreover, the plasma may includechlorine radicals and the plasma control sheet may be formed of anorganic resin, and the plasma control sheet may be a polyimide sheet. Inaddition, tungsten or tungsten silicide surface layer on the substratemay be etched by the plasma.

In accordance with another aspect of the present invention, there isprovided a plasma control member for use in a plasma processingapparatus for converting a processing gas into a plasma by a highfrequency power to perform a process on a substrate mounted on asusceptor by using the plasma in a processing vessel, the memberincluding: a ring member disposed to surround the substrate on thesusceptor; a plasma control sheet disposed on a surface of the ringmember; and an adhesion layer, interposed between the ring member andthe plasma control sheet, for allowing the plasma control sheet to bedetachably attached to the ring member.

The adhesion layer may be an adhesive coated on a rear surface of theplasma control sheet. Further, the plasma control sheet may be formed ofan organic resin, and the plasma control sheet may be a polyimide sheet.

In accordance with still another aspect of the present invention, thereis provided a plasma processing method using a plasma processingapparatus including a ring member disposed to surround a susceptor in aprocessing vessel, the ring member having a plasma control sheetattached on a surface thereof via an adhesion layer, the methodincluding the steps of: loading a substrate on the susceptor; supplyinga processing gas into the processing vessel, converting the processinggas into a plasma by a high frequency power and processing the substrateby using the plasma; and peeling the plasma control sheet off the ringmember and replacing the plasma control sheet with a new one.

The plasma control sheet may contain a material for dissociating acomponent which reacts with a primary active species for the plasmaprocessing. Further, the plasma includes chlorine radicals and theplasma control sheet may be formed of an organic resin, and the plasmacontrol sheet may be a polyimide sheet. In addition, tungsten ortungsten silicide surface layer on the substrate may be etched by theplasma.

EFFECTS OF THE INVENTION

In accordance with the present invention, by configuring the plasmacontrol sheet to be separable from the ring member by interposing theadhesion layer between the ring member and the plasma control sheet, theadhesion of the plasma control sheet to the ring member and the removalof the degraded plasma control sheet from the ring member can beperformed easily. Therefore, the replacement of the plasma control sheetbecomes easy, which relieves an operator from performing cumbersomemaintenance and, also, improves the operating rate of the apparatus.Further, by using a material for dissociating components reactive withan active species which primarily contributes to the plasma processing,for example, by using an organic resin such as a polyimide sheet capableof dissociating carbon radicals, the dissociated components wouldconsume the active species, for example, radicals existing near theperipheral portion of the substrate by reacting with them. Therefore,plasma density around the peripheral portion of the wafer can beprevented from becoming higher than the plasma density around the innerregion. As a consequence, it is possible to perform a plasma processingof a substrate with a superior in-surface uniformity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a plasma processing apparatus in accordance with apreferred embodiment of the present invention, wherein the plasmaprocessing apparatus is utilized as an etching apparatus. Reference 2represents an airtight processing vessel formed of a conductive membersuch as aluminum. A gas exhaust port 21 is formed in a bottom portion ofthe processing vessel 2, and a vacuum exhaust unit, e.g., a vacuum pump22 such as a turbo molecular pump or a dry pump is connected to the gasexhaust port 21 via a gas exhaust line 21 a. Also, a wafer transfer port24 with a gate valve 23 is installed at a sidewall of the processingvessel 2.

Installed inside the processing vessel 2 is an upper electrode 3 alsoserving as a gas shower head for introducing a processing gas, e.g., anetching gas into the vessel 2. The upper electrode 3 is provided in itslower surface with a plurality of gas diffusion holes 31 through whichthe processing gas supplied from a processing gas supply unit 32 via asupply line 33 is sprayed toward the entire surface of a wafer 100disposed below. Further, an insulation member 34 formed of, for example,quartz is disposed to surround the upper electrode 3, so that the upperelectrode 3 is electrically isolated.

Moreover, a susceptor 4 for mounting thereon a substrate is installed inthe processing vessel 2 to face the upper electrode 3. The susceptor 4is electrically isolated from the processing vessel 2 via an insulationmember 40. Also, the susceptor 4 has a cylindrical support 41 formed ofa conductive member such as aluminum, and the support 41 has on its topsurface a mounting plate 42 for mounting the wafer 100 thereon. Themounting plate 42 is a dielectric plate formed of a dielectric materialsuch as ceramic (e.g., aluminum nitride). Inside the mounting plate 42,a thin film shaped electrode (lower electrode) 43 is provided at alocation closer to the upper surface of the mounting plate 42 while amesh-shape heater 44 serving as a heating unit is installed at alocation closer to the lower surface of the mounting plate 42. Further,reference numeral 45 is a gas exhaust ring provided with a number ofperforations in its surface to allow the processing gas to be exhaustedfrom the peripheral portion of the wafer 100 uniformly in acircumferential direction of the wafer 100. Also, though not shown,substrate supporting pins are installed in a way that they can bevertically movable to protrude above and lower below the surface of thesusceptor 4 while supporting the rear surface of the wafer 100. Thetransfer of the wafer 100 between a wafer transfer arm and the susceptor4 is carried out by the cooperation of the wafer transfer arm and thesubstrate supporting pins, the wafer transfer arm entering theprocessing vessel 2 from the outside of the apparatus.

One end of a power supply rod 50 is connected to the lower electrode 43while its other end is coupled to a high frequency power supply 5 via amatching circuit 51. Further, the power supply rod 50 branches out infront of, e.g., the matching circuit 51, and the end of the branch lineis connected to a DC power supply 52 via a switch 53. That is to say,the lower electrode 43 functions as an electrode for the application ofa high frequency voltage and, also, an electrode for an theelectrostatic chuck. Accordingly, the lower electrode 43 and thedielectric portion thereabove jointly form the electrostatic chuck forattracting and holding the wafer 100 electrostatically. Further, theheater is connected to a power supply unit 55 via a conductive bar 54.

A focus ring 6 for controlling plasma is disposed to surround the wafer100 mounted on the mounting plate 42. The focus ring 6 has a ring member61 formed of an insulation member such as quartz, alumina or yttriumoxide, the ring member 61 having a top surface width of about 55 mm.Further, a ring-shaped plasma control sheet 62 is detachably attached onthe top surface of the ring member 61 via an adhesion layer 63, to bedescried later in detail. The plasma control sheet 62 contains amaterial capable of dissociating, e.g., carbon of carbon radicals thatreact with plasma active species, e.g., chlorine radicals when it isexposed to plasma. An example of such a material is an organic resinsuch as polyimide. Further, the sheet 62 is configured to cover theentire top surface of the ring member 61 or to cover it partially with awidth of about 10 to 20 mm, and has a thickness of, e.g., 0.5 to 1 mm.In FIG. 1, the plasma control sheet 62 is disposed to cover the topsurface of the ring member 61 entirely.

Here, the configuration of the plasma control sheet 62 and the adhesionlayer 63 will be described in detail in accordance with the preferredembodiment of the present invention. The rear surface of the plasmacontrol sheet 62 is coated with, for instance, an adhesive, so that theplasma control sheet 62 becomes adhesive and can be stuck to the surfaceof the ring member 61. Further, an operator can peel the control plasmasheet 62 off the ring member 61 by hand. Specifically, a polyimide sheetwhose rear surface is coated with an adhesive can be used as theadhesive plasma control sheet. The inventors learned through experimentsthat “(No. 5414) Polyimide Tape” (product name) manufactured by ScotchInc. can be used, for example. Further, the adhesion layer 63 may not beformed on the entire rear surface of the plasma control sheet 62. Forexample, adhesion layer 63 can be partially formed on the plasma controlsheet 62 by coating an adhesive only on, for example, an outer or innerperipheral portion of the plasma control sheet 62.

During such a process in which a processing gas is converted into plasmaby a high frequency voltage, the inside of the processing vessel 2 ismaintained at a vacuum state to facilitate the generation of the plasma,and the temperature of the processing vessel 2 is set to be high, forexample, about 300° C. Therefore, to prevent the plasma control sheet 62from being separated from the ring member 61 under this condition, thestrength of the adhesive forming the adhesion layer 63 needs to bestrong enough not to be degraded at the high temperature. The Inventorsconfirmed through experiments that a silicon-based adhesive containingSi as its principal component meets such a requirement.

Moreover, the plasma control sheet 62 is preferably provided as close tothe outer edge of the wafer 100 as possible. For example, it isinstalled within a range of 1 mm from the outer edge of the wafer 100.Further, the surface of the ring member 61 is disposed at the same levelas the surface of the wafer 100 or higher than that by, for example, 0.5to 0.7 mm. Accordingly, the plasma control sheet 62 is located higherthan the surface of the wafer 100.

Hereinafter, a method for etching a substrate, e.g., a wafer 100 byusing an etching apparatus with the above configuration and, e.g., achlorine-based processing gas will be described. FIG. 2 illustrates aprocess for etching a barrier metal layer (cap layer) 7 of a gateelectrode. Reference numerals 70 a, 70 b, and 70 c represent a siliconlayer, a gate insulating film formed of, e.g., a SiO₂ film, and apolysilicon layer serving as a gate electrode layer, respectively. Thebarrier metal layer 7 is deposited on top of the polysilicon layer andis formed of, e.g., a tungsten (W) or a tungsten silicide (WSi) layer.Reference numeral 71 is a mask pattern formed of, e.g., resist in apredetermined circuit pattern.

Although there has been described the case of forming a gate electrodeas an example of etching the barrier metal layer 7 formed of a W or aWSi layer, the present invention may also be applied to the case of, forexample, etching a W or WSi layer of a barrier metal layer interposedbetween a wiring layer and an interlayer insulating film. Further, theobject to be etched is not limited to a W or a WSi layer but may be apolysilicon or photoresist layer.

First, a gate valve 23 is opened, and a wafer 100 is loaded into theprocessing chamber 2 through the wafer transfer port 24 from a load lockchamber (not shown). Then, the wafer 100 is placed on the mounting plate42 via the substrate elevating pins (not shown), wherein the mountingplate 42 is heated up to a preset temperature by the heater 44.Afterward, the switch 53 is turned on to apply a DC voltage, which is achuck voltage, to the lower electrode 43, so that the mounting plate 42attracts the wafer 100 electrostatically to hold it on the surfacethereof. Meanwhile, the gate valve 23 is closed and the processingchamber 2 is hermetically sealed.

Subsequently, an etching gas containing, for example, chlorine (Cl₂) andoxygen (O₂) whose flow rates are set as, e.g., 150 sccm and 10 sccm,respectively is injected toward the surface of the wafer 100 via the gasdiffusion holes 31 while vacuum evacuating the processing vessel 2 bymeans of the vacuum pump 22 such that the processing vessel 2 ismaintained at a vacuum level of, for example, 5 to 10 mTorr. The etchinggas injected toward the wafer 100 through the gas diffusion holes 31flows along the surface of the wafer 100 radially outward and isexhausted from the periphery of the susceptor 4 uniformly by beingdispersed due to the presence of the gas exhaust ring 45.

Afterward, if a high frequency voltage of, e.g., 100 MHz for plasmageneration is applied to the lower electrode 43 at, e.g., 250 W from thehigh frequency power supply 5 via the matching circuit 51 and the powersupply rod 50 in order, the high frequency voltage (high frequencypower) is applied between the upper electrode 3 and the wafer 100 loadedon the mounting plate 42, so that the etching gas is converted intoplasma and then, plasma active species serving as etchants, for example,chlorine radicals are generated. Further, a bias voltage of, e.g., 13.56MHz is also applied to the lower electrode at, e.g., 200 W, thusallowing the plasma active species to be projected to the surface of thewafer 100 with high verticality, to thereby etch the portion of thebarrier metal film 7 that is not covered with resist 71 (see FIG. 2B).Furthermore, at an interface between the surface of the plasma controlsheet 62 and a plasma sheath, components reactive with plasma species,for example, carbon radicals in case the plasma control sheet 62 is madeof polyimide, are dissociated from the surface of the plasma controlsheet 62 when the plasma control sheet 62 is exposed to plasma, and thusgenerated carbon radicals react with chlorine radicals existing closelythereabove, i.e., in the vicinity of the peripheral portion of the wafer100, to thereby generate chloride, e.g., CCl_(x) (X=1, 2, 3, 4) havingno etching function. The chloride is exhausted outside the apparatusalong with an exhaust flow.

Then, after a certain period of time, the application of the highfrequency voltage from the high frequency power supply 5 is stopped andthe etching gas is no more injected. Further, a nonreactive gas such asnitrogen is introduced into the processing vessel 2 from a gas supplyunit (not shown), and, at the same time, the vacuum evacuation by thevacuum pump 22 is stopped. Thereafter, the switch 53 is closed to ceasethe application of the chuck voltage, so that the electrostaticadsorption of the wafer 100 is stopped. Subsequently, the gate valve 23is opened and the wafer 100 is unloaded from the etching apparatus,thereby completing the etching process. In addition, when processing anumber of wafers 100 one after another, a new wafer 100 is loaded intothe etching apparatus to undergo the same process as described above.After the operation time of the apparatus reaches, for example, 1000hours while processing multiple wafers 100 repeatedly, a ceiling portionof the processing vessel 2 is opened and maintenance is performed.During the maintenance, the plasma control sheet 62 is peeled off fromthe ring member 61 and is replaced with a new one.

In accordance with the preferred embodiment of the present inventiondescribed above, by making the plasma control sheet 62 separable fromthe ring member 61 by interposing the adhesion layer 63 between the ringmember 61 and the plasma control sheet 62, the attachment of the plasmacontrol sheet 62 to the ring member 61 and the removal of the degradedplasma control sheet 62 from the ring member 61 can be performed easily.Therefore, the replacement of the plasma control sheet 62 becomes easy,which helps the operator in conducting the maintenance work and, also,improves the operating rate of the apparatus. In addition, byconfiguring the plasma control member as the sheet type, themanufacturing cost thereof can be reduced.

Moreover, in accordance with the preferred embodiment of the presentinvention, by forming the plasma control sheet with polyimide capable ofdissociating components reactive with chlorine radicals serving as anetchant which becomes rate controlling factor for facilitating theetching of tungsten or tungsten silicide, carbon radicals dissociatedfrom the polyimide consume the chorine radicals, thereby suppressingdiscrepancies in density of chlorine radicals between the peripheralportion and the inner portion of the wafer W. As a consequence, thewafer 100 can be etched at an etching rate with a superior in-surfaceuniformity.

As for the plasma processing apparatus exposed to the high-temperatureplasma atmosphere, its components tend to be degraded readily and theremay be deposits on the surface of some components. Thus, maintenanceneeds to be performed periodically, for example, every 1000 hours asmentioned above. Further, multiple plasma processing apparatusesfrequently make up a processing system. Accordingly, easy replacement ofconsumable plasma control sheet 62 is very helpful for it reduces theburden of the operator's maintenance work. Here, since the thickness ofthe plasma control sheet 62 is slightly reduced sequentially as itscomponent, e.g., carbon reactive with plasma are dissociated, thethickness of the plasma control sheet 62 should be set to be thickenough to endure until the next maintenance. The inventors found throughsimulations that the thickness of the plasma control sheet 62 necessaryfor operating the apparatus for 1000 hours is 1 mm.

Moreover, since the amount of dissociation of carbon radicals depends onthe surface area of the plasma control sheet 62, if the surface area ofthe plasma control sheet 62 is set to be excessively large, plasmadensity at the peripheral portion of the wafer 100 may be reduced,resulting in deterioration of the in-surface uniformity of plasmadensity. Therefore, by setting the plasma control sheet 62 to have anappropriate surface area, for example, to have a width of 10 to 20 mm inthis preferred embodiment, the plasma density at the peripheral portionof the wafer 100 can be controlled appropriately to thereby enable aprecise control.

Further, the adhesion layer 63 is not limited to being an adhesive. Forexample, adhesion effects may be enhanced through reforming a surface ofthe ring member 61 by, e.g., a photochemical method, i.e., throughsubstituting a hydrophobic C—H bond of the polyimide surface of the ringmember 61 with a hydrophilic group by using a vacuum ultraviolet light(130 nm to 260 nm) and water. Likewise, a laser ablation method may alsobe employed, and the same effect as described above can be obtained.

In accordance with the present invention, in addition to theconfiguration in which the plasma control sheet 62 is provided on theentire surface of the ring member 61 along its circumferentialdirection, it is also possible to arrange plural band-shaped plasmacontrol sheets 62 each having a radial width of, for example, 10 to 20mm at predetermined intervals in the circumferential direction of thering member 61, as shown in FIG. 3. In such a case, components reactiveto plasma, for example, carbon radials can be dissociated from theplasma control sheets 62, so that the same effect as described above canbe obtained. Moreover, though some portions of the surface of the ringmember 61 is exposed to plasma when the plasma control sheets 62 areattached apart from each other at the predetermined intervals, thedegradation of the ring member 61 can be minimized since the carbonradicals dissociated from the plasma control sheet 62 react withchlorine radicals approaching those exposed surface portions of the ringmember 61.

Furthermore, the plasma control sheet 62 may not be disposed to coverthe entire top surface of the ring member 61 but can be disposed only onthe inner peripheral portion of the ring member 61, as shown in FIG. 4.In this case, the same effect as descried above can be obtained as well.

In addition, the present invention is not limited to the configurationin which the plasma control sheet 62 is attached on the flat surface ofthe ring member 61. For example, as shown in FIG. 5, it is possible toform a groove 8 on the top surface of the ring member 61 along thecircumference of the ring member 61 such that the width of the groove 8is substantially equivalent to the width of the plasma control sheet 62.Then, by attaching the plasma control sheet 62 in the groove 8, the sameeffect as described above can be obtained. Further, by adopting thisconfiguration, it is possible to more efficiently prevent edge portionsof the plasma control sheet 62 from peeling off by itself from the ringmember 61 when the processing vessel 2 is evacuated to a vacuum state.Moreover, although the formation of the groove 8 is described for thecase of using the ring-shaped plasma control sheet 62 in this example,it can also be applied to the case of, for example, arranging aplurality of plasma control sheets 62 radially, as illustrated in FIG.3.

Further, the present invention is not limited to the configuration inwhich the plasma control sheet 62 is attached only on the top surface ofthe ring member 61. For example, as shown in FIG. 6, the plasma controlsheet can be disposed to be bent at the inner and the outer edge of thering member 61 to thereby cover the inner and outer side surface of thering member 61 as well as the top surface. In this case, the same effectas described above can also be obtained. Further, by attaching theplasma control sheet on plural surfaces extending in differentdirections, it is possible to more definitely prevent the plasma controlsheet 62 from separating from the ring member 61 when the processingvessel 2 is evacuated to a vacuum state.

Also, the present invention can be applied to various plasma processessuch as a CVD process and an ashing process besides the etching processexemplified in the preferred embodiment.

Hereinafter there will be described examples conducted for investigatingthe effect of the present invention.

EXAMPLE 1

In this example, a wafer 100 was etched by using an etching apparatusincluding a focus ring 6 prepared by attaching an adhesive plasmacontrol sheet 62 formed of a polyimide sheet on the surface of a ringmember 61. Specific processing conditions are as follows. In theexample, the film thickness of the wafer 100 was measured along each ofdiametrical axes (X, Y, V and W axes) extending through the center ofthe wafer W to equally divide the wafer W before and after the etchingprocess. FIG. 7 shows the result of calculating an etching rate at eachmeasurement point. Further, the distribution of chlorine radicals (ratioof intensity between Cl and argon on the surface of the wafer W) wasmeasured, and the result is provided in FIG. 8.

-   -   Target material to be etched: tungsten silicide    -   Etching gas: Cl₂ (150 sccm)+O₂ (10 sccm)    -   Pressure: 5 mTorr        -   Input power (for plasma generation/for bias): 250 W (100            MHz)/200 W (13.56 MHz)    -   Magnetic field: 56 G    -   Temperature: 80° C. (ceiling surface of processing        vessel)/70° C. (sidewall of processing vessel)/60° C. (mounting        plate)

COMPARATIVE EXAMPLE 1

In this example, the same etching process as in Example 1 was conductedby using a focus ring 6 formed of a carbon ring. FIG. 9 shows theresults of calculating etching rates. Further, the results of measuringthe distribution of chlorine radicals in this example is provided inFIG. 8.

COMPARATIVE EXAMPLE 2

In this example, the same etching process was conducted by using a focusring 6 formed of a quartz ring without having a polyimide sheet. Theresults of calculating etching rates and the results of measuring thedistribution of chlorine radicals are provided in FIG. 10 and FIG. 8,respectively.

Results and Analyses of Example 1 and Comparative Examples 1 and 2

As can be seen from the results in FIGS. 7 to 10, in Comparative Example1 using the focus ring formed of the quartz ring, the density ofchlorine radicals at the peripheral portion of the wafer 100 isexcessively high, and the etching rate is also much higher in theperipheral portion than in the central portion of the wafer 100. On theother hand, in both of Example 1 using the polyimide sheet andComparative Example 1 using the carbon ring, the increase in the densityof chlorine radicals and the increase in the etching rate at theperipheral portion of the wafer 100 are small. However, though thedeviations of EE3 mm and EE30 mm are both ±10.6% in the comparativeexample 1, the deviations of EE3 mm and EE30 mm are ±10.2% and ±7.6% inExample 1, respectively, and the increases are also small in Example 1than in Comparative Example 1. Further, EE3 mm refers to an average ofmeasurement values in a region between the edge of the wafer 100 and acircular line inwardly apart by 3 mm therefrom while EE30 mm representsan average of measurement values in a region between the edge of thewafer 100 and a circular line inwardly apart by 30 mm therefrom.

From the above results, by attaching a polyimide sheet on the surface ofthe ring member 61 formed of a quartz ring, it is possible to suppressthe increase in the density of chlorine radicals at the peripheralportion of the wafer 100, and, therefore, the increase of etching ratethereat can also be prevented. It is believed that the increase in thedensity of chlorine radicals at the peripheral portion of the wafer 100can be prevented because carbon radicals dissociated from the polyimidesheet (carbon in Comparative Example 1) react with chlorine radicals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross sectional view of a plasma processingapparatus in accordance with a preferred embodiment of the presentinvention;

FIG. 2 illustrates the surface of a wafer being etched by using theplasma processing apparatus in accordance with the preferred embodimentof the present invention;

FIG. 3 shows a first modification of the focus ring for use in theplasma processing apparatus in accordance with the preferred embodimentof the present invention;

FIG. 4 describes a second modification of the focus ring for use in theplasma processing apparatus in accordance with the preferred embodimentof the present invention;

FIG. 5 illustrates a third modification of the focus ring for use in theplasma processing apparatus in accordance with the preferred embodimentof the present invention;

FIG. 6 shows a fourth modification of the focus ring for use in theplasma processing apparatus in accordance with the preferred embodimentof the present invention;

FIG. 7 presents a characteristic view showing a result of a testconducted to investigate the effect of the present invention;

FIG. 8 depicts a characteristic view showing a result of another testconducted to investigate the effect of the present invention;

FIG. 9 provides a characteristic view showing a result of still anothertest conducted to investigate the effect of the present invention;

FIG. 10 offers a characteristic view showing a result of still anothertest conducted to investigate the effect of the present invention; and

FIG. 11 is a configuration view of a conventional plasma processingapparatus.

DESCRIPTIONS OF REFERENCE NUMERALS

2 processing vessel

22 vacuum pump

3 upper electrode

4 susceptor

42 mounting plate

43 lower electrode

6 focus ring

61 ring member

62 plasma control sheet

1. A plasma processing apparatus for converting a processing gas into aplasma by a high frequency power to perform a process on a substratemounted on a susceptor by using the plasma in a processing vessel, theapparatus comprising: a ring member disposed to surround the substrateon the susceptor; a plasma control sheet disposed on a surface of thering member; and an adhesion layer, interposed between the ring memberand the plasma control sheet, for allowing the plasma control sheet tobe detachably attached to the ring member.
 2. The apparatus of claim 1,wherein the adhesion layer is an adhesive coated on a rear surface ofthe plasma control sheet.
 3. The apparatus of claim 1 or 2, wherein theplasma control sheet contains a material for dissociating a componentwhich reacts with a primary active species for the plasma processing. 4.The apparatus of any one of claims 1 to 3, wherein the plasma includeschlorine radicals and the plasma control sheet is formed of an organicresin.
 5. The apparatus of claim 4, wherein the plasma control sheet isa polyimide sheet.
 6. The apparatus of any one of claims 1 to 5, whereintungsten or tungsten silicide surface layer on the substrate is etchedby the plasma.
 7. A plasma control member for use in a plasma processingapparatus for converting a processing gas into a plasma by a highfrequency power to perform a process on a substrate mounted on asusceptor by using the plasma in a processing vessel, the membercomprising: a ring member disposed to surround the substrate on thesusceptor; a plasma control sheet disposed on a surface of the ringmember; and an adhesion layer, interposed between the ring member andthe plasma control sheet, for allowing the plasma control sheet to bedetachably attached to the ring member.
 8. The plasma control member ofclaim 7, wherein the adhesion layer is an adhesive coated on a rearsurface of the plasma control sheet.
 9. The plasma control member ofclaim 7 or 8, wherein the plasma control sheet is formed of an organicresin.
 10. The plasma control member of claim 9, wherein the plasmacontrol sheet is a polyimide sheet.
 11. A plasma processing method usinga plasma processing apparatus including a ring member disposed tosurround a susceptor in a processing vessel, the ring member having aplasma control sheet attached on a surface thereof via an adhesionlayer, the method comprising the steps of: loading a substrate on thesusceptor; supplying a processing gas into the processing vessel,converting the processing gas into a plasma by a high frequency powerand processing the substrate by using the plasma; and peeling the plasmacontrol sheet off the ring member and replacing the plasma control sheetwith a new one.
 12. The method of claim 11, wherein the plasma controlsheet contains a material for dissociating a component which reacts witha primary active species for the plasma processing.
 13. The method ofclaim 11 or 12, wherein the plasma includes chlorine radicals and theplasma control sheet is formed of an organic resin.
 14. The method ofclaim 13, wherein the plasma control sheet is a polyimide sheet.
 15. Themethod of any one of claims 11 to 14, wherein tungsten or tungstensilicide surface layer on the substrate is etched by the plasma.